Nowadays, the market is supplied with a variety of folding knives. As is well known, a folding knife uses a resilient plate to assist in driving out the blade. Referring to FIGS. 1A and 1B, the folding knife 1 includes a blade 11, a handle 13, and a resilient plate 15. The blade 11 has one end pivotally connected to a first end of the handle 13 so that the blade 11 can rotate about the pivotally connected position either into or out of the handle 13. A stud, or pushing post, 111 is provided on the blade 11, adjacent to the aforesaid end thereof, and located outside the handle 13. The resilient plate 15 has a first end positioned near the other end (hereinafter, the second end) of the handle 13 and a second end extending to a position adjacent to where the handle 13 and the blade 11 are pivotally connected. When the blade 11 is completely received in the handle 13, the resilient plate 15 presses against the aforesaid end of the blade 11. More particularly, the portion of the resilient plate 15 that presses against the blade 11 applies a first force A thereto (as indicated by the dashed-line arrow A in FIG. 1A), and the first force A tends to rotate the blade 11 further into the handle 13. Consequently, the blade 11 is firmly positioned in the handle 13. Once the blade 11 is rotated out of the handle 13 by a predetermined angle (about 4 to 8 degrees), the resilient plate 15 applies a second force B to the blade 11 (as indicated by the dashed-line arrow B in FIG. 1B), causing further rotation of the blade 11 out of the handle 13. As a result, the blade 11 spins instantaneously and completely out of the handle 13.
As shown in FIGS. 1A and 1B, the resilient plate 15 can press against different parts of the blade 11 and apply different forces thereto to either hold the blade 11 securely in the handle 13 or speed up rotation of the blade 11 out of the handle 13. Therefore, when it is desired to rotate the blade 11 from inside the handle 13 to the outside, the user only has to push the pushing post 111 with a thumb, thereby rotating the blade 11 out of the handle 13 by the predetermined angle (about 4 to 8 degrees), and the blade 11 will rotate instantly and completely out of the handle 13 in away similar to a switchblade.
Apart from the aforesaid design, it is feasible to replace the resilient plate with a spiral spring as the element that assists in pushing the blade, and this replacement is demonstrated in FIG. 2, in which most of the elements are identical to those in FIGS. 1A and 1B and are therefore identified by the same reference numerals as in FIGS. 1A and 1B. The spiral spring 21 in FIG. 2 is provided where the blade 11 is pivotally connected to the handle 13. The spiral spring 21 constantly applies to the blade 11 a force that tends to rotate the blade 11 out of the handle 13. When the blade 11 is completely received in the handle 13, a detent unit (not shown) on the handle 13 holds the blade 11 and applies another force thereto such that the blade 11 is positioned in the handle 13. To rotate the blade 11 out of the handle 13, the user only has to push the pushing post 111 on the blade 11 to overcome the force applied by the detent unit and disengage the blade 11 from the detent unit, and the blade 11 will rotate rapidly out of the handle 13 due to the force applied by the spiral spring 21 to the blade 11.
Referring again to FIGS. 1A to 2, while the folding knife 1 may use either the resilient plate 15 or the spiral spring 21 to push the blade 11, a user cannot rotate the blade 11 out of the handle 13 without applying a force to the pushing post 111. Hence, even if the folding knife 1 is carried by the user in a pocket and subjected to impact while the user is walking or doing exercise, the blade 11 will not spin out. After all, the folding knife 1 is so configured that unless the pushing post 111 is pushed to rotate the blade 11 out of the handle 13 by the predetermined angle (about 4 to 8 deuces) or unless the blade 11 is disengaged from the detent unit on the handle 13, the blade 11 cannot pop out of the handle 13, and this is the major difference between the folding knife 1 undo switchblade, whose blade will spring out as soon as a button is touched or pressed. Nevertheless, the inventor of this patent application has found the following drawbacks of the folding knife 1 in use. First of all, the pushing post 111, which a user must push with a thumb to drive the blade 11 into rotation, only has a limited length; therefore, the top end of the pushing post 111 is pretty close to the outer surface of the handle 13, making it difficult for the user to push the pushing post 111 and open the knife with a single hand. This is especially true of one who has never used the folding knife 1 before. Thus, the convenience of the folding knife 1 is seriously compromised. Furthermore, given the limited length of the pushing post 111, the user's thumb must be very close to one lateral surface of the blade 11 while pushing the pushing post 111. Also, as the blade 11 spins rapidly out of the handle 13, the user's thumb is within the rotation range of the blade 11. Such close proximity of the thumb to the blade 11 may result in cutting injury and create a sense of fear in those who are using the folding knife 1.
With the conventional folding knives still having problems in use, the issue to be addressed by the present invention is to overcome the aforesaid shortcomings of the prior art, provide greater convenience of use, and effectively eliminate the risk of injury during use.